182 PRIMITIVE TYPES OF INTELLIGENCE 
conclusions. A starfish may possibly acquire. habits of a 
certain kind, but it is not proven that it is able to form 
associations. 
We do not intend to deny the existence of intelligence in 
the groups mentioned; we think it not improbable that 
intelligence of a primitive sort may be discovered, at least 
in the more highly developed members of these divisions; 
but at the present time we can only grant the Scotch verdict 
of “not proven.” 
In the Arthropoda instinctive activity is frequently re- 
presented as reaching its culmination, and some investigators 
have gone so far as to assert that the behavior of these animals 
is made up entirely of instincts and reflexes. This opinion 
is in part based on a priori deductions from the organization 
of the nervous system and it is held to chiefly by morpholo- 
gists and physiologists whose observation of the behavior of 
animals is limited and warped by preconceptions. 
Bethe, who has done a large amount of thorough and 
valuable work on the anatomy and physiology of the nervous 
system of arthropods, and who has very successfully employed 
the results of these investigations in the analysis of normal 
behavior, was led to the somewhat extreme position of 
denying, not only associative memory, but consciousness 
as well, in all the arthropods. The complex behavior of 
these forms, according to him, can be analyzed in terms of 
reflex action, and there is consequently no ground for assum- 
ing any psychic elements whatsoever in these animals. 
At the close of his important memoir on the nervous 
system of the crab Carcinus menas, there are described a 
few experiments which convinced Bethe that this animal 
is unable to profit by experience. Bethe placed a crab in an 
aquarium containing a devil fish, Eledone, which took up 
its station in a dark corner. The crab when placed in the 
